In digital printing, a known tradeoff exists between printing efficiency and printing flexibility. Digital printing (as opposed to offset printing) may involve the use of printers having printable page or web widths large enough to accommodate multiple publication pages side-by-side, referred to as N-up printing. N is the number of columns printed across the width of a web or other print medium. For example, if the web width can accommodate two publication pages side-by-side, this is referred to as 2-up; three pages side-by-side is referred to as 3-up, etc. The pages from the printer are then directed into a finishing device which separates (slits) publication page “columns” and then cuts the publication pages from each other, and then sorts and stacks the pages.
If the publication pages across the web are from a single copy of a single publication, the finishing device performs an operation referred to as slit-merge and all of the publication pages from the N-up web are sorted and ordered into a single stack for binding. Slit-merge refers to a method of finishing that accepts N-up web print output, cuts (slits) the web into pages, merges these pages into a single stack, and outputs this single stack with physical offsetting representing a logical break in output (e.g., a book, set of books).
If the publication pages across the web are from different publications or parallel copies of the same publication, the finishing device performs an operation referred to as slit-stack and the publication pages from the N-up web are sorted into N stacks. Slit-stack refers to a method of finishing which accepts N-up web print output, cuts (slits) the web into pages, and outputs N stacks of output, each stack representing a logical break in output (e.g., a book, set of books, or portion of a book).
For on-demand printing of single copies of individual publications (quantity 1, Print on Demand or POD), it would be desirable that slit-merge finishing be used so that these single copies could be sequentially printed, slit, sorted and segregated by the finishing device. However, current slit-merge finishing devices and methods are limited to 2-up printing. For 3-up printing, only slit-stack finishing technology is available. Consequently, there is no efficient method of performing on-demand printing of single copies of individual publications in an N-up mode where N is greater than 2. In addition, slit-stack technology is much less complex and paper-handling intensive than slit-merge technology. Therefore, as printer manufacturers support wider print webs, finishing equipment manufacturers develop slit-stack finishing technology for higher “N-up” values long before they develop slit-merge finishing technology for the same “N-up” value.
To provide efficient and cost effective high volume POD manufacturing, several technological advancements have been developed by digital printer hardware and finishing hardware manufacturers, including high volume POD production control and printer management and wide (e.g., 19″+) paper web support. However, printers have not been able to realize the full potential of these advances because they have been limited to 2-up slit-merge printing, 2-up slit-stack printing, and 3-up slit stack printing.